Poly(vinyl chloride) resins, which are known as resins having a satisfactory balance among various properties including transparency and mechanical properties, have conventionally been used in various applications because the glass transition temperatures thereof can be regulated in a wide range according to applications by means of a plasticizer and various compounding ingredients. In recent years, however, replacement of poly(vinyl chloride) resins with other resins is being investigated enthusiastically from the standpoints of environmental issues, etc. Among promising resins expected to be usable as substitutes for poly(vinyl chloride) resins are polycarbonate resins, which are excellent in transparency, heat resistance, and impact resistance. Polycarbonate resins are being utilized in various applications.
Polycarbonate resins are generally produced using bisphenols as a monomer ingredient, and are being extensively utilized as so-called engineering plastics in the fields of electrical/electronic parts, automotive parts, medical parts, building materials, films, sheets, bottles, optical recording media, lenses, etc. so as to take advantage of the superiority thereof such as transparency, heat resistance, and mechanical strength.
However, the conventional polycarbonate resins deteriorate in hue, transparency, and mechanical strength when used over a long period in places where the resins are exposed to ultraviolet rays or visible light. There hence have been limitations on outdoor use thereof and on use thereof in the vicinity of illuminators.
Furthermore, use of the conventional polycarbonate resins as various molded articles has encountered a problem that the polycarbonate resins show poor mold release characteristics during melt molding and it is difficult to use the resins as transparent materials, optical materials, or the like. Polycarbonate resins have a high melt viscosity and low flowability and, hence, have had a drawback that the resins have poor moldability when sheets, films, molded articles, and the like are molded therefrom. Especially with respect to use in optical applications, polycarbonate resins are currently usable only in limited applications because polycarbonate resins have a high photoelastic coefficient and are apt to cause a phase difference upon stress imposition thereon.
Techniques in which a benzophenone-based ultraviolet absorber, benzotriazole-based ultraviolet absorber, or benzoxazine-based ultraviolet absorber is added to a polycarbonate resin in order to overcome such problems are widely known (for example, non-patent document 1).
It is also widely known that addition of a hindered amine-based light stabilizer (HALS) to a polycarbonate resin is impracticable because polycarbonate resins are unstable to basic ingredients, e.g., alkalis, even at ordinary temperature and are hydrolyzed also by HALSs.
The bisphenol compounds for use in producing conventional polycarbonate resins have a benzene ring structure and hence show high absorption of ultraviolet rays. This leads to a deterioration in the light resistance of the polycarbonate resins. Consequently, use of monomer units derived from an aliphatic dihydroxy compound or alicyclic dihydroxy compound which has no benzene ring structure in the molecular framework or from a cyclic dihydroxy compound having an ether bond in the molecule, such as isosorbide, is expected to theoretically improve light resistance. In particular, polycarbonate resins produced using, as a monomer, isosorbide obtained from biomass resources have excellent heat resistance and mechanical strength, and many investigations thereon hence have come to be made in recent years (for example, patent documents 1 to 7).
It is also widely known that benzotriazole, benzophenone, and cyanoacrylate compounds and the like are added as ultraviolet absorbers to polycarbonate resin compositions obtained using monomers having an ether bond in the molecule, such as isosorbide, isomannide, and isoidide, which each have no benzene ring structure in the molecular framework (for example, patent document 8).
Many resin compositions of a polycarbonate resin with a polyester resin have hitherto been proposed in order to improve the moldability of polycarbonate resins. For example, patent document 9 discloses a resin composition obtained by mixing a polycarbonate resin with a polyester resin such as poly(butylene terephthalate) or poly(ethylene terephthalate), and patent document 10 discloses a resin composition which has improved flowability imparted thereto by controlling the degree of transesterification of a polycarbonate resin with a polyester resin and which is excellent in transparency, solvent resistance, and impact resistance. Furthermore, patent document 11 and patent document 12 disclose resin compositions each constituted of a polycarbonate resin and an amorphous polyester resin.